sorry for my late reply and many thanks for the replies.
But yesterday I had a chance to test this again. First, I updated to latest firmware 0.76.
There was no change in the behaviour.
@marqs: “You’ll need to access adv.timing and copy 1024×768 parameters into 1280×1024 mode to fix this.” -> how can I do this? I was playing around with the menu in order to change some parameters (without any impact). Where do I need to apply your fix exactly?
The Turbo Chameleon itself can be configured to produce different outputs (I think default mode is 800×600@72Hz). So it’s worth trying to change the output there as well.